Particle size and percent solids monitor

ABSTRACT

This invention relates to a method and apparatus for developing signals representative of the size and number of particles, such as ore in a slurry. In a preferred form, the invention comprises directing two beams of ultrasonic energy through the slurry, each beam operating at a different frequency and with the beam frequencies so chosen that the attenuation of each beam is a different function of the percent solids by volume, the geometric means particle diameter, the standard deviation of the distribution of the particles and the largest sized particles in the slurry. The two signals resulting therefrom are compared and processed electronically so as to provide two output signals, one of which indicates the particle size and the other, the percent solids by volume in the slurry.

United States Patent 1191 Cushman et al.

[451 Dec. 18, 1973 1 PARTICLE SIZE AND PERCENT SOLIDS MONITOR [73]Assignee: Autometrics Co., Boulder, C010.

[22] Filed: Nov. 23, 1971 [21] Appl. No.: 201,504

Related U.S. Application Data [63] Continuation-in-part of Ser. No.866,976, Oct. 16,

I969, abandoned.

205,356 1/1968 U.S.S.R. 73/432 PS Primary Examiner-S. Clement SwisherAttorney-Anderson, Spangler & Wymore 5 7 ABSTRACT This invention relatesto a method and apparatus for developing signals representative of thesize and number of particles, such as ore in a slurry. In a preferredform, the invention comprises directing two beams of ultrasonic energythrough the slurry, each beam operating at a different frequency andwith the beam frequencies so chosen that the attenuation of each beam isa different function of the percent solids by volume, the geometricmeans particle diameter, the standard deviation of the distribution ofthe particles and the largest sized particles in the slurry. The twosignals resulting therefrom are compared and processed electronically soas to provide two output signals, one of which indicates the particlesize and the other, the percent solids by volume in the slurry.

57 Claims, 40 Drawing Figures PATENTED DEC] 81875 SHiEI 030! 33 QQQQH000A mDwHmK/ mUZMMMDUUO .mO BEDOEM quaale u eouaxxnooo 3o TouenbaxgINVENTORS CHARLES R. CUSHMAN JAMES C. HALE VERNON A Mia M AN ERSON 925ATTOR PATENTEUUEEI 8 191a 3,7790. 0

SHEEI OQUF 33 SIZE ATTENUATION IN db 3 3 m H R SIIVENOSs qp NI Nomvnmmvsamo S ACLUE H VERNON A AN ERSON PATENTEUDEBWISIS 3.779.070

SHEET USUF 33 I SIZE ATTENUATION IN db CHARLES R.CUSHMAN JAMES C.HALEVERNON ASI W ERSON M41 @yf PATENTEU WI] 8 ms SHEET OBBF 33 SIZEATTENUATION IN db AN ERSON 925 A'ITOR S H? NI NOICLVUNFLTI-LV SCII'IOSPATENTED 81975 3.779 .070

SHEET 07 0F 33 1 SIZE ATTENUATION IN db Arrenuai'ion Versus PercenT byVolume of Sol ids Pima Samp les Series 10 Speci fic Gravify SizeFrequency So! i ds Frequency 45% 200 mesh L, 3 uwsm'o s p NI NOILVHNHLLVsamos q' L VERNON Aim ERSON ?%TFORW PATENTEUUEC 1 81973 SHEET 08F 33SIZE ATTENUA'IION IN db mo 30m 216m 33 E EwuLmm mnmLw co mscmfg qp NINOIJJVONHLLLV SGIIOS INVENTORS CHARLES RCUSHMAN JAMES C. HALE VERNON APATENTEDUEBI 81m 3.779.070

SHEET 10 0F 33 SIZE ATTENUATION IN db Pima Samp Ies Series IOO SpecificGraviTy 2.74 Si ze Frequency l6 |8.3 Sol ids Frequency 50% 200 mesh qpNI NOILVHNHLLV SGI'IOS INVENTORS CHARLES R.CUSHMAN JAMES C.HALE VERNONA9194 ERSON W/ ATTORW PAIENTED 0501 8 ms SHEEI 11 0F 33 5. 8 im 0 0m .ILm iom a INVENTORS CHARLES R. CUSHMAN JAMES C. HALE VERNON A Maw y m ANERSON wfi A'I'I'OR S ,PYATENTEDUEDIBISIYS v I 3,179,070. v @sum mar 33PARTICLE DIAMETER IN MICRONS .2 ,3 .4 .5 .SIJJISI '2 speci fvl c Gravi'ry Frequency CHARACTERISTIC ATTENUATION ,OF-A SINGLEPARTICLE I versus PARTICLE DIAMETER v INVENTORS CHARLES R.CUSHMYAN JAMES C. HALE VERNONA N VERSON PATENTEDUEBI 8l973 3,779,070

sum 17 or 3 SMJHDIW NI EDMINEHO HAEIS SEL .110 HHLHWVICI 1356 microns1M0) 2.29 M 217.6 microns .57

X measured poims F105 error HBHWHN HSBW SERIES HAEIS GHVUNVIIS m VENTORSCHARLES RCUSHMAN JAMES C.HALE VERNON A915 ERSON I f rrorzw PATEIHEU3,779,070

SHEET 18 0F 33 CHARLES R.CUSHMAN JAMES C.HALE VERNON Aim ERSONPATENTEDUEEIBIUYB 3,779,070

sum 19 or 33 vll In N

A D v C 0; 0; a 5 A A H 4 INVENTORS CHARLES R.CUSHMAN JAMES C.HALEVERNON AFERSON

1. A particle size distribution monitor which comprises a source ofultrasonic energy, transducer means connected to said source andpositioned to transmit and receive a beam of ultrasonic energy through acontinuous flowing fluid sample containing a known percent by volume ofparticles in suspension, means adapted to make an instantaneousmeasurement of the attenuation of the beam in passing through the slurryand develop a single output signal representative of the total particlesize distribution of the sample.
 2. The particle size distributionmonitor of claim 1 wherein the transducer means includes a transmittertransducer and a receiver transducer with the transmitter beingpositioned to transmit ultrasonic energy through a fluid containingparticles in suspension and the receiver being positioned to receive thetransmitted signal.
 3. The particle size distribution monitor of claim 1including air stabilizing means adapted to stabilize the entrained airin a sample being measured.
 4. The particle size distribution monitor ofclaim 1 including agitation means adapted to establish and maintainsubstantially uniform particle suspension in the slurry.
 5. A particlesize distribution monitor which comprises a first source of ultrasonicenergy, transducer means connected to said first source and positionedto transmit and receive a first beam of ultrasonic energy through afluid containing particles in suspension, means adapted to measure theattenuation of said first beam in passing through the slurry and developan output signal representative thereof, a second source of ultrasonicenergy operating at a frequency different from the first source, saidtransducr means being connected to said second source in timed relationwith the connection of the transducer with said first source andpositioned to transmit and receive a second beam of ultrasonic energythrough the fluid containing particles in suspension, means adapted tomeasure the attenuation of said second beam in passing through theslurry and develop an output signal representative thereof and means formodifying one output signal with the other output signal to produce aresultant signal representative of the particle size distribution of thesuspended particles.
 6. The particle size monitor of claim 5 wherein thetransducer means connected to said first and second sources ofultrasonic energy is positioned such that the ultrasonic beams lie inthe same plane.
 7. The particle size monitor of claim 5 wherein thefrequency of one source is selected such that the attenuation thereof asa function of shift in particle size distribution of suspended particlesis substantially constant.
 8. The particle size monitor of claim 5wherein the transducer means includes a transmitter transducer and areceiver transducer with a transmitter being positioned to transmitultrasonic energy through the fluid containing particles in suspensionand a receiver being positioned to receive the transmitted signal. 9.The particle size distribution monitor of claim 5 including airstabilizing means adapted to stabilize the entrained air in a samplebeing measured.
 10. The particle size distribution monitor of claim 5including agitation means adapted to establish and maintainsubstantially uniform particle suspension in the slurry.
 11. Theparticle size monitor of claim 5 including a transducer means connectedto each of said two sources of ultrasonic energy.
 12. A particle sizedistribution monitor which comprises a source of ultrasonic energyadapted to generate two ultrasonic signals of different frequencies,transducer means connected to said ultrasonic source positioned andadapted to transmit and receive a beam of one ultrasonic frequency andthen another in timed relation therewith through a fluid containingparticles in suspension, means adapted to measure the attenuation ofeach beam in passinG through the slurry and develop an output signalrepresentative thereof and means for modifying one output signal withthe other output signal to produce a resultant signal representative ofthe particle size distribution of the suspended particles.
 13. Theparticles size monitor of claim 12 wherein one frequency of the sourceis selected such that the attenuation thereof as a function of shift inparticle size distribution of suspended particles is substantiallyconstant.
 14. The particle size distribution monitor of claim 12including air stabilizing means adapted to stabilize the entrained airin a sample being measured.
 15. The particle size distribution monitorof claim 12 including agitation means adapted to establish and maintainsubstantially uniform particle suspension in the slurry.
 16. Theparticle size monitor of claim 12 wherein the transducer means connectedto said source of two beams of ultrasonic energy is positioned such thatthe ultrasonic beams lie in the same plane.
 17. A particle sizedistribution monitor according to claim 12 including a further source ofultrasonic energy adapted to generate ultrasonic energy at one otherfrequency, transducer means connected to said further source positionedand adapted to transmit and receive a beam of ultrasonic energy throughsaid fluid containing particles in suspension, means adapted to measurethe attenuation of said beam in passing through the slurry and develop afurther output signal representative thereof and means for modifying thefurther output signal with one of said other output signals to produce aresultant signal representative of the percent by volume of solids inthe slurry.
 18. The particle size monitor of claim 12 wherein thetransducer means includes a transmitter transducer and a receivertransducer with a transmitter being positioned to transmit ultrasonicenergy through the fluid containing particles in suspension and areceiver being positioned to receive the transmitted signal.
 19. Aparticle size and percent solids monitor which comprises a source ofultrasonic energy, transducer means connected to said source andpositioned to transmit and receive a beam of ultrasonic energy through afluid containing particles in suspension, means adapted to measure theattenuation of the transmitted beam in passing through the fluidcontaining particles in suspension and produce an output signalrepresentative thereof, means for measuring percent solids adapted todevelop an output signal representative of the percent solids in thefluid containing particles in suspension and modifying one output signalwith the other output signal to produce a resultant signalrepresentative of the particle size distribution of the suspendedparticles.
 20. The particle size and percent solids monitor of claim 19,wherein the frequency of the ultrasonic energy is selected such that theattenuation of the ultrasonic beam differs significantly as the particlesize distribution of the suspended particles becomes more corase or morefine.
 21. The particle size and percent solids monitor of claim 19,wherein the frequency of the ultrasonic energy is selected such that theattenuation of the ultrasonic beam is due substantially toscattering-loss wherein the attenuation increases with the particle sizedistribution of the suspended particles becoming more coarse anddecreases with the particle size distribution of the suspended particlesbecoming more fine.
 22. The particle size distribution monitor of claim19 including air stabilizing means adapted to stabilize the entrainedair in a sample being measured.
 23. The particle size distributionmonitor of claim 19 including agitation means adapted to establish andmaintain substantially uniform particle suspension in the slurry. 24.The particle size and percent solids monitor of claim 19 wherein themeans of measuring percent solids comprises a second source ofultrasonic energy, transducer means connected to said second source andpositioned to Transmit and receive a beam of ultrasonic energy throughthe fluid containing particles in suspension and means adapted tomeasure the attenuation of the transmitted beam passing through thefluid containing particles in suspension and produce an outputrepresentative thereof, wherein the frequency of the second source ofultrasonic energy is selected to be at a frequency different from thefirst source and such that the attenuation thereof is substantiallyunaffected by typical changes in particle size distribution in aparticular fluid suspension of particles.
 25. The particle size andpercent solids monitor of claim 19 wherein the means of measuringpercent solids comprises a second source of ultrasonic energy,transducer means connected to said source and positioned to transmit andreceive a beam of ultrasonic energy through the fluid containingparticles in suspension and means adapted to measure the attenuation ofthe transmitted beam passing through the fluid containing particles insuspension and produce an output representative thereof, wherein thefrequency of the first source of ultrasonic energy is selected such thatthe attenuation of the ultrasonic beam is due substantially to viscousloss, scattering loss and/or diffraction loss and the frequency of thesecond source of ultrasonic energy is selected such that the attenuationof the ultrasonic beam as a function of changes in particle size issubstantially constant.
 26. The particle size and percent solids monitorof claim 19 wherein the means of measuring percent solids comprises asecond source of ultrasonic energy adapted to be connected to thetransducer means in timed sequential relation to the connection theretoof the first source of ultrasonic energy and the frequency of the secondsource of ultrasonic energy is selected to provide a substantiallyconstant attenuation of the transmitted signal as a function of shift inthe particle size distribution of the suspended particles.
 27. Theparticle size and percent solids monitor of claim 24 wherein thefrequency of the first source of ultrasonic energy is selected to be ata higher frequency than the frequency of the second source.
 28. Theparticle size and percent solids monitor of claim 25 wherein thefrequency of the first source of ultrasonic energy is selected to be ata frequency higher than that of the second source.
 29. The particle sizeand percent solids monitor of claim 25 wherein the frequency of thefirst source of ultrasonic energy is selected such that the attenuationof the ultrasonic beam is due substantially to scattering-loss whereinthe attenuation increases with the particle size distribution of thesuspended particles becoming more coarse and decreases with the particlesize distribution becoming more fine. attenuation
 30. A particle sizemonitor which comprises a first source of ultrasonic energy adapted togenerate a first frequency, transducer means connected to said firstultrasonic source positioned and adapted to transmit and receive a firstbeam of ultrasonic energy through a fluid containing particles insuspension, means adapted to measure the attenuation of the transmittedbeam in passing through the fluid containing particles in suspension andproduce first output signal representative thereof, a second source ofultrasonic energy adapted to generate a second frequency different fromsaid first, transducer means connected to said second ultrasonic sourcepositioned and adapted to transmit and receive a second beam ofultrasonic energy through the fluid, means adapted to measure theattentuation of the transmitted beam passing through the fluidcontaining particles in suspension and produce a second output signalrepresentative thereof, and means for modifying said first output signalwith said second output signal to produce a resultant signalrepresentative of the particle size distribution of the suspendedparticles.
 31. The particle size monitor of claim 30 including a thirdsource of ultrasonic energy adapted to gEnerate a third frequency,transducer means connected to said third source positioned and adaptedto transmit and receive a third beam through the fluid containingparticles in suspension, means adapted to measure the attenuation of thethird beam in passing through the slurry and develop a third outputsignal representative thereof and means for modifying said third outputsignal with a selected one of said first and second output signals toproduce another resultant signal representative of the percent by volumeof particles in the fluid suspension.
 32. The particle size distributionmonitor of claim 30 wherein the transducer means includes a transmittertransducer and a receiver transducer with the transmitter beingpositioned to transmit ultrasonic energy through a fluid containingparticles in suspension and the receiver being positioned to receive thetransmitted signal.
 33. The particle size distribution monitor of claim30 including air stabilizing means adapted to stabilize the entrainedair in a sample being measured.
 34. The particle size distributionmonitor of claim 30 including agitation means adapted to establish andmaintain substantially uniform particle suspension in the slurry. 35.The particle size monitor of claim 30 wherein the transducer meansconnected to said first and second sources of ultrasonic energy ispositioned such that the ultrasonic beams lie in the same plane.
 36. Amethod of monitoring the particle size distribution of particlessuspended in a fluid medium under dynamic conditions which comprises thesteps of transmitting a first beam of ultrasonic energy of one frequencythrough the fluid containing suspended particles, detecting theattenuated beam after passing therethrough, developing a first signalrepresentative of the attenuation of the first beam, transmitting asecond beam of ultrasonic energy of a different frequency than the firstthrough the fluid containing suspended particles, detecting theattenuated beam after passing therethrough, developing a second signalrepresentative of the attenuation of the second beam and modifying saidfirst signal with said second signal to produce a resultant signalrepresentative of the particle size distribution of the suspendedparticles.
 37. The method of claim 36 wherein the frequency of one ofsaid beams of ultrasonic energy is selected such that the attenuationthereof is due substantially to scattering-loss wherein the attenuationincreases with particle size distribution of the suspended particlesbecoming more coarse and decreases with the particle size distributionof the suspended particles becoming more fine.
 38. The method of claim36 wherein the frequency of one of said beams of ultrasonic energy isselected to provide a substantially constant attenuation of thetransmitted signal as a function of shift in particle size distributionof the suspended particles.
 39. The method of claim 36 wherein thefrequency of the first beam of ultrasonic energy is selected such thatthe attenuation of the ultrasonic beam is due substantially to viscousloss, scattering loss and/or diffraction loss.
 40. The method of claim36 including the step of stabilizing any entrained air in the fluidsuspension.
 41. The method of claim 36 including the step of agitatingthe sample to establish and maintain a substantially uniform particlesuspension in the slurry.
 42. The method of claim 36 includingtransmitting a third beam of still another frequency through the fluidcontaining suspended particles, detecting the attenuated beam afterpassing therethrough, developing a third signal reprsentative of thethird beam and modifying the third signal with a selected one of saidfirst and second signals to produce another resultant signalrepresentative of the percent by volume of particles in fluidsuspension.
 43. A method of monitoring the particle size distribution ofparticles in a fluid medium under dynamic conditions which comprises thesteps of transmitting a beam of ulTrasonic energy through the fluidcontaining suspended particles, detecting the attenuated beam afterpassing therethrough, developing a first output signal representative ofthe attenuation of the beam, measuring the percent by volume ofparticles in suspension and developing a second output signalrepresentative thereof modifying said first output signal with thesecond output signal to produce a resultant signal representative of theparticle size distribution of the suspended particles.
 44. The method ofclaim 43 wherein the frequency of the beam of ultrasonic energy isselected such that the attenuation of the ultrasonic beam is duesubstantially to viscous loss, scattering loss and/or diffraction loss.45. A method of monitoring the particle size distribution of particlessuspended in a fluid medium under dynamic conditions which comprises thesteps of transmitting a beam of ultrasonic energy through the fluidcontaining suspended particles, maintaining the percent by volume ofparticles in suspension substantially constant, detecting the attenuatedbeam after passing therethrough, and developing a signal representativeof the attenuation of the beam and of the particle size distribution.46. The method of claim 45 including the step of stabilizing anyentrained air in the fluid suspension.
 47. The method of claim 45including the step of agitating the sample to establish and maintain asubstantially uniform particle suspension in the slurry.
 48. A method ofmonitoring the particle size distribution of particles suspended in afluid medium under dynamic conditions which comprises the steps oftransmitting a first beam of ultrasonic energy through the fluidcontaining suspended particles, detecting the attenuated beam passingthrough the fluid containing suspended particles, developing a firstsignal representative of the attenuation of the first beam, transmittinga second beam of ultrasonic energy of a frequency different than thefirst through the fluid, developing a second signal representative ofthe changes in attentuation of the second ultrasonic beam as a functionof changes in solids content of the fluid containing suspendedparticles, and modifying one output signal with the other output signalto produce a resultant signal representative of the particle sizedistribution of the suspended particles.
 49. A method of monitoring theparticle size and percent solids distribution of particles suspended ina fluid medium according to claim 48 wherein the second signal isdeveloped as a function of a received beam of ultrasonic energytransmitted through the slurry, the frequency of which is selected toprovide a substantially constant attenuation of the transmitted signalswith shifts in the particle size distribution of the suspendedparticles, such that the second signal is representative of theattenuation resulting from changes in percent by volume of solids in thefluid containing particles in suspension.
 50. The method of claim 48wherein the frequency of the first and second source of ultrasonicenergy are selected such that the difference between the frequenciesthereof is sufficient to produce readily distinguishable attenuationlevels therebetween in passing through a slurry of suspended particlesto be measured.
 51. The method of claim 48 wherein the frequency of thefirst source of ultrasonic energy is selected such that the attenuationof the first source of ultrasonic energy is due substantially to viscousloss, scattering loss and/or diffraction loss and the frequency of thesecond source of ultrasonic energy is selected such that the attenuationof the ultrasonic beam as a function of changes in particle size issubstantially constant.
 52. The method of claim 48 wherein the frequencyof the first source of ultrasonic energy is selected to be higher thanthe frequency of the second source of ultrasonic energy.
 53. The methodof claim 48 wherein the frequency of the first source of ultrasonicenergy is selected such that the atteNuation of the ultrasonic beam isdue substantially to scattering loss wherein the attenuation increaseswith particle size distribution of the suspended particles becoming morecoarse and decreases with the particle size distribution becoming morefine.
 54. The method of claim 48 including the step of stabilizing anyentrained air in the fluid suspension.
 55. The method of claim 48wherein the frequency of the first beam of ultrasonic energy is selectedsuch that the attenuation of the ultrasonic beam is due substantially toviscous loss, scattering loss and/or diffraction loss.
 56. The method ofclaim 49 including the step of stabilizing any entrained air in thefluid suspension.
 57. The method of claim 49 including the step ofagitating the sample to establish and maintain a substantially uniformparticle suspension in the slurry.